Thickener for hydrocarbon fuels



2,769,697 Patented Nov. 6, 1956 THICKENER FOR ROCARBON FUELS No Drawing. Application April 29, 1953, Serial No. 352,065

Claims. (Cl. 44-7) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

This invention relates to incendiary fuels, to thickening agents therefor and to ways and means whereby stability, uniformity and consistency of these products may be improved.

More particularly this invention relates to the improvement of the stability, consistency and over-all performance of known incendiary gels and thickeners therefor by the addition of alumina aerogel thereto.

During the last war, sources of rubber were cut off and the rubber, required to thicken or gel gasoline and similar liquid hydrocarbon fuels to produce incendiary gels of many military uses, was not available. It became necessary to resort to other types of gelling agents. A satisfactory class of thickeners were developed, which would produce the desired consistencies of incendiary fuel gel. The desired consistency, of course, varies according to the manner in which the incendiary gel is to be employed. For instance, a higher viscosity is generally desired for shell and hand grenade fillings than for flame thrower fillings wherein the incendiary must be projected under pressure through a nozzle and hurled through the air for a substantial distance in the form of a stream. As the result of much experience and experimentation it has been found desirable, and at times, necessary to impart controllable consistencies to the fuel gel to be used, depending upon the manner of contemplated use.

A class of soap thickeners have been developed which have been used successfully in the gelling of gasoline, kerosene or other liquid hydrocarbon fuel for incendiary use. The more successful thickening agents of this class of soaps are aluminum soaps of fatty acids and particularly coprecipitated aluminum soaps of mixed acids such as mixtures of coconut acids and naphthenic acid, as well as mixtures containing oleic acid. Fieser U. S. Patent No. 2,606,107 and Minich U. S. Patent No. 2,390,609, exemplify this class of soap thickeners for gasoline and other liquid hydrocarbon fuels. The popular name for a thickener of this type is napalm. Unfortunately this class of thickening agents and the gels formed therewith, are not ideal in that they do not have the desired stability as to their consistency, particularly when in contact with chemical agents. The gels tend to liquefy or separate out on slight increases in their moisture content, to thicken when chilled and to become more mobile when heated. It has also developed that these thickeners, and the incendiary gels derived therefrom, are not sufiiciently resistant to the deleterious effects of xylenol, amines, potassium acetate, acid soldering flux and other substances to which they are, at times exposed during the processes of compounding, and the storage and preparation for use in the field. It has also been found that free fatty acids contained in the napalm thickener tend to peptize the mixture.

Many attempts have been made, heretofore, to stabilize these incendiary compositions with additives, heat and chemical treatments. Among other things, a large number of well-known dehydrating crystals and granules have been tried out in various ways, but in each case the dehydrating agent used introduced new difiiculties. Magnesium sulfate formed hard scales and flakes, broke down the gel and was exceedingly slow in reaching an equilibrium in the composition. Other dehydrating agents proved less efiective. None of the crystal and granular dehydrating agents would maintain the desired consistency under both arctic and tropical temperature conditions which vary from 40 to F. Further, none of these agents would maintain the required consistency in the presence of the chemical agents above which tend to deteriorate the gel.

Many of the difficulties encountered in the use of napalm thickeners have been overcome by the use of a silica gel additive as proposed by Bauer and Broughton, U. S. application Serial No. 765,644; the use thereof tends to prevent the breakdown of fuel gels when they are subjected to exploded powder gases or to the deleterious effects of alcohols, phenols, amines, potassium acetate, soldering flux and various rust preventatives with which the gels become physically associated during production, storage, and use.

er and does not remove this peptizing material.

It is, therefore, the object of our invention to improve the known incendiary gels which include thickeners of.

the napalm type to obtain a stabilized consistency.

It is an object to provide thickeners having stabilized. consistency, particularly in the presence of moisture and deleterious chemical agents.

It is a further object to provide means and a process; whereby the consistency of incendiary fuel gels and thick-- ening agents therefor may be increased and stabilized against chemical agents.

It is a further object to improve the process whereby napalm thickeners are produced.

It is a particular object to increase the consistency and to improve the chemical stability of incendiary gels, and thickeners therefor, beyond that which is obtained by the addition of silica gel thereto.

We have found that alumina aerogel is a superior ad ditive to napalm thickeners. This material when added with napalm to gasoline, kerosene or other liquid hydrocarbon fuels causes a marked, and unexpected, increase in the consistency and stability of the resultant gels. In addition, the alumina aerogel is an effective grinding aid and anti-agglomerant in the preparation of finely ground napalm powder. Napalm powder ground with alumina aerogel exhibits thickening in liquid hydrocarbon fuels, superior to napalm powder alone as well as to napalm powder ground with silica gel.

In the proposal to improve the gel consistency of napalm thickened liquid hydrocarbon fuels by the addi tion of silica gel, it is believed that the action of the silica gel is mechanical in nature. Alumina aerogel, on the other hand, not only possesses mechanical absorbent activity but also is capable of reacting chemically with the free fatty acids contained in the napalm thickener to remove this peptizing material and, at the same time, to create additional aluminum soap which adds its thickening power to that of the original napalm. The alumina aerogel is also believed to improve the thickening power by contributing additional aluminum to oxygen linkages thereby increasing the chain lengths in the gel structure. While we are not to be bound by this theory as to the unexpected improvement exhibited by the use of alumina.

aerogel, its outstanding action is readily demonstrated.

The silica gel, however, does not react: with any free fatty acids contained in the napalm thicken- 1. By first adding the alumina powder to the napalm.

powder and grinding the mixturein standard equipment, suchas a ball mill, to obtainan intimate blend. Then adding the blend to a liquid hydrocarbon fuel to;.obtain a gel.

2. By first forming a suspension of the alumina in the liquid. hydrocarbon fuel, followed by addition of the napalm powder to the suspension to obtain a gel.

Procedure 1 above is preferred since the advantageous, unexpected properties of the alumina gel-as a grinding aid and anti-agglomerant are thus utilized to the fullest extent.

Our invention can be applied to all soap thickeners to be used to gel liquid hydrocarbon fuels but we have found that the addition of alumina gel is most beneficial with aluminum soaps of fatty acids and particularly with napalm thickener. Napalm is generally considered to embrace the acid mixture and the aluminum salt mixture of fatty acids found in coconut oil together with approximately an equal amount of one or more of the following compounds; unsaturated fatty acids having from 17 to 22 carbon atoms such as oleic and linoleic acids, and naphthenicvacid. One such composition is the aluminum salts of the acids in the following proportions:

Parts by weight It may be tabilized against oxidation by the addition of alpha-naphthol to the sodium soap used to prepare the aluminum soap. It is described more fully in Joint Army- Navy Specification, JANN589, April 30, 1948. v The alumina aerogel may be added to the soap thickenerwithin the range of 0.5 to 25% by weight of the aerogel to 99.5 to 75% by weight of the soap. In the preferred embodiment, 5% by weight of alumina aerogel is employed with 95% by weight of napalm to form a thickener-for gasoline. The thickener may be added to the gasoline fuel in varying percentages, from 6 to 12% by weight being the normal range.'

The preferred method for the preparationof our improved incendiary fuel gel is set forth in the example becated at any time for test purposes. This test gasoline has the following composition:

Percent by weight Benzene. 18 Cyclohexane 20 7 Normal heptane 57 Isooctane (2,2,4-trimethyl-pentane) 5 low which is presented by Way of illustration and not of j limitation.

Example 95 grams of napalm (conforming to Joint Army-Navy Specification JAN-N-589,produced by the Imperial Paperand Color. Corporation) and 5 grams of'aluminum; aerogel,(produced by the process of Kistler-J. Phys. 7

to the time required to overcome settling. The gel was then stored.

The test gasoline. used in this example is a synthetic blend of hydrocarbons which has a composition similar to thegasolines .used in the production of incendiary fuel gels. This blend has properties, for. gelation purposes, very closely approximating those of ordinary gasoline .but is used in place thereof because it can be exactly dupli- To demonstrate the superior performance of alumina aerogel over napalm alone and over'the proposedsilica aerogel as an additive to napalm thickeners, the following comparative test was run. The comparison was made by grinding the napalm samples with. the aerogel as in the example above, employing 95 parts by weight of napalm to 5 parts by weight of the aerogel. The gels were formed with each napalm sample by the formation of 6% concentration thereof inthe test gasoline. The Gardner consistency was determined by the standard mobilometer method after 24 hours storage at roonrtemperature. (The test procedure is'outlined in Specification IAN-I- 711, December 16, 1948). The silica aerogel is that known as Santocel C (Monsanto). I

Aerogel Napalm Gel in Test Gasoline Type Conoentra- Gardner tion in consistency Nap (a) percent It is apparent that alumina-modified napalm thickener is far superior to silica-modified thickener. I This superiority in fuel gel consistency, coupled with its stability, toward moisture and the chemical agents encountered in processing, storage and use, and with theability to neutralize free fatty acids in. napalm" definitely establishes alumina areogel as an outstanding additive for napalm thickeners, Theimprovementin grinding characteristics,

of napalm containing alumina is also of. great benefit in the processing of the thickener. i a

We claim:

1. In theproduction .of an incendiary-liquid hydrocarbon fuel gel thickened with an aluminum soap thickener, the improvement which comprises the inclusion therein of alumina aerogel in the proportion of 0.5 to 1 25 parts by weight of aluminav gel, to 99.5 to parts by weight of the soap thickener to stabilize the thickened fuelgel toward the deleterious action of chemicalre:

agents.

2. In the production of a thickened incendiary fuel: gel, comprising essentially a coprecipitated aluminum. soap. of mixed naphthenic acid, oleic acid and coconut 1 fatty acids and gasoline, the improvement which comprisesthe-inclusionof about 0.3% byweight of alumina aerogel to stabilize the thickened fuel'gel toward the del-. eterious action of chemical agents;

3. Aathickener for incendiary liquidhydrocarbonfuel gels consisting essentially of an; aluminum ,soap thick:

ener containing between 0.5 to 25% by weight of alumina aerogel.

4. A thickener for gasoline consisting essentially of a. coprecipitated aluminum soap of 'mixed, naphthenic acid, oleic and coconut'fatty acids and about 5%- by weight of alumina aerogel.

5. The process for preparing, an-improvedstabilized thickener for liquid hydrocarbon fuels which comprises.

grinding an aluminum soapthickener with betweenq0.5

and 25 ,byweight of alumina aerogel until an intimate blend is obtained- 6. The process of claim 5 wherein the ,soap thickeneris a coprecipitated aluminum soap;.of ,mixed -naphthenic acid, oleic acid and coconut fatty acids.

10. The process of claim 9 wherein the weight of the alumina aerogel is about 5% of the weight of the soap thickener.

5 References Cited in the file of this patent UNITED STATES PATENTS 2,606,107 Fieser Aug. 5, 1952 2,625,508 Stross Jan. 13, 1953 10 2,684,339 Herron July 20, 1954 

1. IN THE PRODUCTION OF AN INCENDIARY LIQUID HYDROCARBON FUEL GEL THICKENED WITH AN ALUMINUM SOAP THICKENER, THE IMPROVEMENT WHICH COMPRISES THE INCLUSION THEREIN OF ALUMINA AEROGEL IN THE PORPORTION OF 0.5 TO 25 PARTS BY WEIGHT OF ALUMINA GEL, TO 99.5 TO 75 PARTS BY WEIGHT OF THE SOAP THICKENER TO STABILIZE THE THICKENED FUEL GEL TOWARD THE DELETERIOUS ACTION OF CHEMICAL REAGENTS. 